Titanium dioxide has been employed as an attenuator of ultraviolet light in a wide range of applications such as sunscreens, organic resins, films and coatings.
It is well known that UVA radiation contributes primarily to premature skin ageing, whilst UVB radiation is the predominant cause of skin cancer. Currently, almost all commercially available titanium dioxide products attenuate predominantly in the UVB region. Whilst these titanium dioxide products may give some UVA attenuation, many final end-use sunscreen products need to incorporate inorganic UVA absorbers such as zinc oxide and/or organic UVA absorbers such as butyl methoxydibenzoylmethane (avobenzone) in order to obtain the required broad spectrum UV protection. The demand for sunscreen products with improved UVA efficacy and a high UVA/UVB ratio has increased recently with the new European Union Commission requirements for all sunscreen products to have a UVA protection which is at least one third of the label SPF value.
In addition, the demand for “inorganic only” sunscreens has increased in recent years, due to concerns over the toxicity of various organic UV absorbers, and the “yellowing” impact some organic UV absorbers have on inorganic sunscreens. The requirement for an alternative to zinc oxide has also developed due to legislation restricting the use of zinc oxide, and the relatively low UV attenuation and/or transparency of zinc oxide.
Thus, there is a need for a particulate titanium dioxide which exhibits effective UVB absorption properties, but also has a high UVA efficacy, and acceptable aesthetics when applied to the skin, e.g. transparency and/or skin feel.